Polymeric materials with “smart” behavior have the potential for wide applicability in a variety of fields. The presence of non-covalent, reversible interaction in these materials shows differential behavior when exposed to an external stimulus such as temperature, pressure, change in pH, etc. Many interactions are used to self-assemble molecules into supramolecular materials. These include hydrogen bonding interactions, pi-pi interactions, donor-acceptor interactions, metal-ligand interactions, etc. Appropriate design of the supramolecular molecule can facilitate the organization of the constituent molecule and express their functionality in the final material.
Organic electronic devices are found in a variety of electronic equipment. In such devices, an organic active layer is sandwiched between two electrical contact layers. The active layer emits light upon application of a voltage bias across the contact layers.
Many types of luminescent devices exist, including a number of all solid state devices. Solid state devices are preferable over incandescent or fluorescent bulbs in that they are lighter, more compact, can be made smaller, and can have higher efficiency. Examples of solid state luminescent devices include, for example, light emitting diodes (LEDs), such as gallium arsenide or silicon carbide LEDs, organic light emitting diodes (OLEDs), and polymeric devices typically referred to as polymer light emitting diodes (PLEDs).
OLED/PLED devices typically comprise (a) a thin film structure comprising a transparent electrode, usually indium doped tin oxide (ITO) on a glass or plastic support layer, where the ITO is optionally coated with polyaniline or poly(ethylenedioxythiophene) (PEDOT), (b) one or more organic containing layers, (c) a hole conducting layer, for example, of a triphenylamine derivative, (d) a luminescent layer, for example, a polyphenylenevinylene derivative or a polyfluorene derivative, (e) an electron conducting layer, for example, an oxadiazole derivative, and (f) a second electrode, for example, calcium, magnesium, aluminum, and the like.
OLED and PLED devices are typically lightweight, potentially low cost (although this has yet to be demonstrated commercially), can be fabricated as a thin film, flexible structures, have a wide viewing angle, and exhibit high brightness. The disadvantages of these devices are the short device lifetimes, increasing voltages when operated in a constant current mode, and broad spectral widths.
There is still a need for materials that may be suitable for light emitting applications and in luminescent devices.